Method of dispersing asphalt



Patented ar. 6, 1934 METHQD 0F DISPERSING ASPHALT August E. Sehutte, Northboro, Mass, assignor to The Lane Construction Corporation, Meriden, Conn, a corporation of Connecticut No Drawing. Application October 30, 1933, Serial No. 695,849

14 Claims.

This invention relates to aqueous dispersions of asphalt, such for example as are usable in road building. Such dispersions have been previously proposed and manufactured but they have been unsatisfactory for one reason or another. One objection common to most of the previously proposed dispersions is that they are limited to the use of naturally soft or artificially softened asphalts. A second objection likewise common to most of the methods was that the protective colloid used as a dispersing agent produced a skin coating on the asphalt particles, or otherwise affected their nature, so that the asphalt particles had at least a portion of their normal adhesiveness destroyed upon coagulation. Since the main use of the emulsion is the application of asphalt for use as a binder, this destruction of normal adhesiveness reduced the utility of the material for its intended purpose. A further difficulty with some of the previous dispersing processes has been that the coagulating step was reversible, so that a sudden rain after the application of the material to a road would have disastrous effects. Certain of the prior dispersing agents have had the additional difficulty of being readily subject to fermentation, this being true particularly of the starches and mealy material sometimes employed.

I have found that these disadvantages may be avoided, and an improved product obtained at a less cost, by the use of the process described below. The dispersion obtained by my improved process is stable and not subject to rapid fermentation, sothat the expense of preservatives may be greatly reduced or even avoided. Upon evaporation of the water the particles of dispersed asphalt coalesce irreversibly, producing asphalt having its qualities substantially unchanged. Furthermore, the process employs as a dispersing agent a material having at present no substantial commercial utility, and which can be obtained from a standard commodity without in any way interfering with the normal commercial employment of that commodity. By this process harder asphalt may be dispersed than with prior methods, it being unnecessary to soften or cut back these hard asphalts by the use of solvents.

This application is a continuation in part of my prior application Serial No. 669,077, filed May 2, 1933.

According to my new process the asphalt in a heated state is added to an aqueous extract of the hulls of linseed or flaxseed. The hulls of these seeds, as contrasted with their mealy and oil-containing interiors, carries a mucllaginous substance which is extractible from the hulls by hot water. This mucilaginous material when in aqueous solution acts as a protective colloid having a wholly novel eiiect when used to form an asphalt dispersion. With previous asphalt dispersion processes the actual dispersing step has been quite critical, resulting in many losses of whole batches of material when the optimum conditions were not rigidly adbored to. Using the hull extract of flaxseed as a dispersing agent the conditions of dispersion are no longer critical, and the resulting dispersed product is stable to the shocks of transportation and to climatic variations in temperature. The mealy portion of the seeds is not a satisfactory dispersing agent and is actually detrimental to the resulting product. A method of extraction of the mucilaginous component which avoids the presence of the mealy constituents of the seeds is therefore employed, such as boiling the seeds while whole or boiling the hulls by themselves.

In practicing the improved process by one method I first boil whole flaxseed in water to remove the mucilaginous matter which is carried by the hulls. A suitable proportion for the initial extraction of mucilaginous matter is oneha1f pound of seed per gallon of water. The resultant solution, after the settling of the seeds, is clear and transparent. After the removal of the seeds from the extract of the mucilaginous material, which may be done by decantation or filtering, the seeds can be dried and employed in the usual manner for the extraction of oil; the residual meal being usable for feed as is customary. In fact, the quality of the meal is improved by the removal of the mucilaginous material, the purgative efiect of which has previously been detrimental. It should be observed that the normal use of the seeds is interfered with in no way by this process, the material used being extracted from the hulls only. For ordinary commercial purposes the dried seeds after the extraction of the mucilaginous matter are indistinguishable in utility from the ordinary linseed of commerce.

It is also important to note that the extract is uncontaminated with the oily or mealy portions of the seeds, thereby avoiding the presence in the coalesced asphalt of an undesirable residuum and also avoiding the fermentation which occurs in an aqueous mixture of these portions unless a relatively large amount of preservative is added. Any slight amount of oil which is carried over appears as a scum on the top of the liquid and about 15 minutes.

preferably-in a hot state,

can readily be skimmed ofl. Furthermore, the elimination of these oily and mealy constituents permits the mucilaginous material to form a homogeneous, continuous film around the asphalt particles and greatly increases the stability of the dispersion.

A second and preferred manner of obtaining the mucilaginous extract is to employ the hulls alone. In the manufacture of linseed oil the seeds are passed between a succession of pairs of rollers to crush them and to express the oil. During this process the hulls are capable of being separated from the mealy and oily portions of the seeds by Winnowing or by simply screening upon a screen of 16-20 meshes per inch. At this stage the hulls are not coated substantially with oil, and separate cleanly, being retained by the screen as relatively large bran-like flakes. The mealy residue may then be returned to the usual linseed oil process, and will produce a better oil than the. usual crushed seed containing the hulls.

The hulls, in the form of flakes substantially free from the other constituents of the seed, are then boiled in water until they are substantially freed from the mucilaginous material which they carried. A suitable proportion is 3 ounces of hulls to a gallon of Water, this giving a suitable concentration for use as a dispersing agent. According to the commercial process at present preferred the hulls are placed in water, the water is brought to a boil, and the boiling maintained for The hulls are preferably removed by filtration or decantation while hot. The boiling is much less critical than Where the whole seeds are used, since there are no other parts of the seed present to be considered. Fur- 'thermore, it has been found that the hulls free their mucilaginous constituent much more freely than the whole seeds, and are easier to separate by decantation or filtering from the resulting aqueous extract; Due to these features it is possible to prepare a relatively strong solution of' the mucilaginous extract where the hulls rather than the whole seeds are used, this solution then being capable of dilution with hot water to the concentration desired. Indeed, on account of the fact that the hulls can be purchased on pound of mucilaginous material, much more cheaply than the seeds, and that they are much easier to handle throughout both the boiling and a basis, per

separating steps, it is in general a more satisfactory method to follow. a

To this aqueous extract of mucilaginous matter, 7 the asphalt is added, softened by heat until it will pour and work easily. Agitation of the asphalt in the mucilaginousextract may be accomplished by any ordinary mixing means. The amount of asphalt added and the degree of breaking up of the asphalt in the mixing process will depend upon the use to which M the dispersion is to be put. For the binding of coarse aggregates a coarser dispersion of greater concentration is preferred, while for binding fine aggregates a finely subdivided dispersion of less "concentration will work better.

The resulting dispersion is in all cases stable, and irreversible when the water has been evaporated. The muci- 'laginous mat*er used as a dispersing agent has no apparent effect upon the asphalt particles after the evaporation of the water, these particles retaining all the adhesiveness that the asphalt possessed before dispersion. When the asphalt has been dispersed, the dispersion can bethinned by the addition of water to produce the consistency desired. The addition of a small amount ea ers (about 0.1 to 0.2%) of sodium hydroxide or other alkali to the extract before the asphalt is added will increase the facility of the dispersing process, and is preferred. 7

The dispersion process above described has been found in practice to be substantially independent of the temperature at which dispersion takes place, except that the asphalt should be hot enough to give it fluidity. The hull extract is preferably used Warnnbut may be used at any temperature from atmospheric to boiling. The dispersion should not be placed in storage while very near the boiling point, as it has in that case a tendency to cream or partially separate, but with this exception the dispersion process proceeds substantially independently of the temperature conditions, the manner of mixing, or the speed of addition of the asphalt to the extract. Dispersions have been made in a pail using a stick as a mixing agent, in a tank with paddle stirrers, and in specially constructed dispersion mixers with practically equal facility. Batches of sec gallons or over are easily made every fifteen minutes.

The resultant dispersion also has novel charwith present commercial standards, the per cent of solid residue due to the extract in the coagulated asphalt being of the order of instead of 23% as is permitted by present commercial specifications. The new dispersion seems also to be independent of freezing or of the jars and shocks of transportation both of which frequently caused undesired coagulation of previous dispersions.

Among. the advantages of this dispersion is the facility with which the physical characteristics of the dispersion can be changed. In the use of dispersed asphalt in roadways it is very desirable to change the physical characteristics of the dispersion, as for different degrees of penetration different rluidities are required. For a fine road material a thinner dispersion can be used, while for a coarse material where it is required to keep the asphalt as near the top as possible a more viscous materialis necessary. Again, different viscosities are required if the material is to be mixed in place or is to be mixed in a mixer. Up to the present time these physical characteristics could only be changed by the addition of more or less Water, which carried with it the fault of setthe dispersion is used; and third, by changing the type of dispersion as will be made clear below.

The present-day emulsions of soap and clay and asphalt are only slightly affected by temperature changes, while the hull seed extract is readily changed by temperature. and therefore can be used both in its. thinnest state while hot (up to 175 F), or can be used at a great density The concentration of the extract is in all cases extremely low as contrasted asphalt in the gel.

(around F.). Furthermore, the physical characteristics of the dispersion itself can be readily changed so as to produce an easily breaking or a hard breaking dispersion.

Two distinct types of dispersion can be produced. If, for instance, the dispersion described above be made, a compound is produced which has an inner or disperse phase of asphalt and an outer or continuous phase of a gel comprising water and the hull extract. This outer phase can be thinned by the addition of hot water, and upon cooling will still remain the outer phase or the continuous phase of the dis persion. If, however, a moderate amount of cold water is added to the cold dispersion the freshly added water will be dispersed along with the If still morewater is added a still new condition is produced in which the asphalt globules coated with the gel are the interrupted phase, while the freshly added water is the continuous phase. This is due to the fact that thegel is not soluble in cold water. The dispersion in which the additional water is present as a disperse phase has great fluidity and a rapid break, so that it is useful where a heavy asphalt deposit is required and breaking or coagulation of the dispersion within a relatively short period is desired.

I am aware that vegetable mucilages have been suggested as an emulsifying agent or protective colloid in dispersions. They are, however, not suitable as a class for the dispersion of asphalt for use in roadways. One of the principal reasons the relatively large amounts of them which is necessary to disperse the asphalt and hence the relatively large solid residue which is left after the dispersion is broken down. A gel produced from linseed hull extract has a characteristic not shown by any other vegetable extract with which I am familiar. It has a cohesive action which can be best compared with that shown by egg albumen, the whole mass moving as a unit rather than as an ordinary liquid. Agaragar produces a gel which lacks this quality and could be by comparison described as a short gel,- that is, a weak solid; while Irish moss produces a slightly different gel-which also lacks the characteristics of hull extract. The same thing holds good as far as gum tragacanth is concerned; while gum arabic produces a still different gel. None of them in any way resemble the hull extract gel which perhaps can be described best as being arr-extraordinarily cohesive liquid. For example, if a gel of linseed hull extract having 0.4% of solid matter be taken at room temperature (say below 80 F.) it can be poured over the edge of a vessel an inch or more without breaking off, and will return into the vessel when the vessel is righted. While it is difficult to state theoretical conclusions with confidence when materials of the complex and uncertain characteristics of linseed hull extract are concerned, and particularly in the field of colloidal chemistry, it is my belief that the remarkable effect of this product is due to this extreme cohesiveness, which gives a strength and protecting action to the gel far in excess of any other protective colloid with which I am familiar, when equivalent weights are considered. Whatever may be the reason, it is a fact that dispersed asphalt may be made by the use of linseed hull extract with concentrations of the protective colloid far below that necessary with other vegetable extracts. It is this property of strong protective effect in slight concentration, rather than any theoretical explanation of it, that is the main distinguishing feature of the protective colloid which I employ. For the production of the dispersed asphalt by my method gels containing from to of solid can be used, while Irish moss requires 5% for making a somewhat similar product, while agar-agar up to 10% has been tried without success. Gum tragacanth requires about 7%, while gum arabic requires 6%. Not only does a large amount of these materials have to be used for the dispersion of the asphalt, but the dispersions are difficult to make and the excess amount of foreign matter destroys to a great extent the usefulness of the dispersion,not only by destroying the adhesiveness and ductility of the asphalt itself, but by giving an asphalt coating, after it has set and dried, which can be re-emulsified by the addition of water, especially on a roadway, where the combination of water and attrition will re-emul sify the coating. The asphalt dispersionprepared with linseed hull extract, on the contrary, while extremely stable in dispersed form, contains so little solid dispersing agent after coagulation that it cannot be re-emulsified. The dispersing power of the hull extract in low concentrations results in a very small amount of foreign substance being present around the asphalt particles at the instant of coalescence; this foreign matter being distributed at that time as an extremely thin coating which cracks readily and permits complete coalescence of the asphalt particles.

The active principle of the linseed hull extract is not easily isolated in pure form, and is uncertain and complex in its exact chemical character. For this reason, I have described its action and properties in detail and have given one commercial source and its preferred method of preparation. I do not wish to exclude from the scope of my invention, however, the use of this active principle whether obtained from the described source and by the described method or otherwise. As pointed out above, the exact proportions of the ingredients may be varied to suit the particular specifications for the dispersions being made. The invention is thus not to be limited to any particular proportions except as pointed out in the following claims.

I claim:

1. An aqueous dispersion of asphalt in which the water constitutes the continuous phase and in which the continuous phase contains the mucilaginous component of fiaxseed hulls and is substantially free from any other component of the flaxseed.

2. An aqueous dispersion of asphalt in which the water constitutes the continuous phase, and in which the continuous phase contains the mucilaginous hull extract of fiaxseed substantially free from other components of the iiaxseed.

3. An aqueous dispersion of asphalt having as its continuous phase an alkaline gel composed of water and the mucilaginous component of flaxseed hulls and substantially free from any other component of the fiaxseed, and having asphalt as its disperse phase.

4. A dispersed asphalt having as its continuous phase a gel composed substantially entirely of water and the mucilaginous substance found in flaxseed hulls, said substance having substantially the aqueous solubilty and the viscosity and cohesiveness in solution of the aqueous extract of flaxseed hulls substantially free from any other component of the iiaxseed, and having asphalt and water as separate disperse phases,

the dispersed water being present in a sufficient quantity to substantially reduce the viscosity of the composite dispersion.

5. A dispersed asphalt having as its continuous phase the aqueous extract of the mucilaginous component of flaxseed hulls substantially free from any other component of the flaxseed, and having water and asphalt as separate disperse phases. ,6.'A dispersed asphalt having as its continuous phase a gel composed substantially entirely of water and less than one-half of one per cent of the mucilaginous substance found in flaxseed hulls, said substance having substantially the aqueous solubility and the viscosity and cohesiveness in solution oi' the aqueous extract of fiaxseed hulls substantially free from any other com ponents of the flaxseed, said mucilaginous substance being soluble in hot water but substantially insoluble in cold water, said gel having a strongly cohesive viscosity at temperatures below, F., and having asphalt as the disperse phase.

7. A dispersed asphalt having as its, continuous phase a gel composed substantially entirely of water and the mucilaginous substance found in flaxseed hulls, said mucilaginous substance having substantially the aqueous solubility and the viscosity and cohesiveness in solution of the aqueous extract of flaxseed hulls substantially free from any other component of the fiaxseed, said dispersion having asphalt as its dispersed phase. 7

8. A process of preparing an aqueous dispersion of hard asphalt, in which the Water is to constitute the continuous phase, whichcomprises boiling whole flaxseeds in water to extract the mucilaginous component from the hulls thereof without removing the oily or other constituents of the seeds, removing the seeds from the mucilaginous solution thus resulting, adding to the mucilaginous solution a small amount of alkali and asphalt softened by heat without substantial admixture of softening materials to the asphalt, commingling the asphalt and solution to cause the asphalt to be dispersed, and thinning the resultant dispersion by the addition of water.

9. A process of preparing an aqueous. dispersion of asphalt, in which the water is to constitute the continuous phase, which comprises extracting the mucilaginous component from the hulls of flaxseed by subjecting said hulls to the action of heated water and without removing the .oily or other constituents of the seeda'adding to 'while hot, and without any substantial admixture of solvent, with a previously prepared solution in water or" the mucilaginous component of fiaxseed substantially free from any other component of the fiaxseed.

11. A process of preparing an'aqueous dispersion of asphalt, in which the water is to comprise the continuous phase, which comprises separating the hulls of flaxseed from the remainder of the seed, subjecting said hulls to the action of heated water to extract their mucilaginous component, separating the hulls from the extract, adding a small amount of alkali and heated asphalt to the extract, and commingling the asphalt with the extract to cause its dispersion.

12. A process of preparing an aqueousdispersion of asphalt, in which the Water is to comprise the continuous phase, which comprises separating the hulls. of flaxseed from the remainder of the seed,'subjecting said hulls to the action of heated water to extract their mucilaginous component, separating the hulls from the extract, adding heated asphalt to the extract, and commingling the asphalt with the extract to cause itsdispersion. V

13; A method of producing an asphalt dispersion which comprises dispersing asphalt in an aqueous extract of the mucilaginous component of flaxseed hulls substantially free from any other component of thefiaxseed, and, when said dispersion is below the temperature of solubility in water of said mucilaginous component, cornmingling therewith water also below said temperature.

14. A method of producing an asphalt dispersion which comprises dispersing asphalt in an aqueous extract of the mucilaginous component of fiaxseed substantially free from any other component of the fiaxseed, and, when said dispersion is below the temperature of solubility of said mucilaginous component, commingling therewith water also below said temperature and in an amount below that permitting the water to become the continuous phase of thedispersion, whereby said water and asphalt will both be dispersed in acontinuous phase composed of said extract.

AUGUST E. SCI-IUTTE. 

